- ID:
- ivo://CDS.VizieR/J/ApJ/759/11
- Title:
- Wolf-Rayet content of M31
- Short Name:
- J/ApJ/759/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Wolf-Rayet (WR) stars are evolved massive stars, and the relative number of WC-type and WN-type WRs should vary with the metallicity of the host galaxy, providing a sensitive test of stellar evolutionary theory. However, past studies of the WR content of M31 have been biased toward detecting WC stars, as their emission-line signatures are much stronger than those of WNs. Here, we present the results of a survey covering all of M31's optical disk (2.2deg^2^), with sufficient sensitivity to detect the weaker-lined WN types. We identify 107 newly found WR stars, mostly of WN type. This brings the total number of spectroscopically confirmed WRs in M31 to 154, a number we argue is complete to ~95%, except in regions of unusually high reddening. This number is consistent with what we expect from the integrated H{alpha} luminosity compared to that of M33. The majority of these WRs formed in OB associations around the Population I ring, although 5% are truly isolated. Both the relative number of WC- to WN-type stars as well as the WC subtype distribution suggest that most WRs exist in environments with higher-than-solar metallicities, which is consistent with studies of M31's metallicity. Although the WC to WN ratio we find for M31 is much lower than that found by previous studies, it is still higher than what the Geneva evolutionary models predict. This may suggest that Roche-lobe overflow produces the excess of WC stars observed at high metallicity, or that the assumed rotational velocities in the models are too high.
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- ID:
- ivo://CDS.VizieR/J/ApJ/655/851
- Title:
- Wolf-Rayet galaxies in the SDSS
- Short Name:
- J/ApJ/655/851
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a large sample of 174 Wolf-Rayet (W-R) galaxies drawn from the Sloan Digital Sky Survey to study whether and how the slope of the stellar initial mass function depends on metallicity. We calculate for each object its oxygen abundance, according to which we divide our sample into four metallicity subsamples. For each subsample, we then measure three quantities: the equivalent width of the H{beta} emission line, the equivalent width of the W-R bump around 4650{AA}, and the W-R bump-to-Hbeta intensity ratio, and compare to the predictions of the same quantities by evolutionary synthesis models of Schaerer & Vacca (1998ApJ...497..618S).
- ID:
- ivo://CDS.VizieR/J/A+A/439/265
- Title:
- Wolf-Rayet population in M83
- Short Name:
- J/A+A/439/265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of non-nuclear regions containing Wolf-Rayet stars in the metal-rich spiral galaxy M 83 (NGC 5236). From a total of 283 candidate regions identified using He II {lambda}4686 imaging with VLT-FORS2, Multi Object Spectroscopy of 198 regions was carried out, confirming 132 WR sources. From this sub-sample, an exceptional content of ~1035+/-300 WR stars is inferred, with N(WC)/N(WN) ~ 1.2, continuing the trend to larger values at higher metallicity amongst Local Group galaxies, and greatly exceeding current evolutionary predictions at high metallicity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/420/3091
- Title:
- Wolf-Rayet population in NGC 5068
- Short Name:
- J/MNRAS/420/3091
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a narrow-band Very Large Telescope/Focal Reduced Low-dispersion Spectrograph #1 imaging survey of the SAB(rs)cd spiral galaxy NGC 5068, located at a distance of 5.45Mpc, from which 160 candidate Wolf-Rayet sources have been identified, of which 59 cases possess statistically significant {lambda}4686 excesses. Follow-up Gemini Multi-Object Spectrograph spectroscopy of 64 candidates, representing 40 per cent of the complete photometric catalogue, confirms Wolf-Rayet signatures in 30 instances, corresponding to a 47 per cent success rate. 21 out of 22 statistically significant photometric sources are spectroscopically confirmed.
- ID:
- ivo://CDS.VizieR/J/MNRAS/381/418
- Title:
- Wolf-Rayet population in NGC 1313
- Short Name:
- J/MNRAS/381/418
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a VLT/FORS1 survey of Wolf-Rayet (WR) stars in the spiral galaxy NGC 1313. In total, 94 WR candidate sources have been identified from narrow-band imaging. Of these, 82 have been spectroscopically observed, for which WR emission features are confirmed in 70 cases, one of which also exhibits strong nebular HeII{lambda}4686 emission. We also detect strong nebular HeII{lambda}4686 emission within two other regions of NGC 1313, one of which is a possible supernova remnant. Nebular properties confirm that NGC 1313 has a metal content log(O/H)+12=8.23+/-0.06, in good agreement with previous studies. From continuum-subtracted H{alpha} images we infer a global star formation rate of 0.6M_{sun}/yr. Using template LMC WR stars, spectroscopy reveals that NGC 1313 hosts a minimum of 84 WR stars. Our census comprises 51 WN stars, including a rare WN/C transition star plus 32 WC stars. In addition, we identify one WO star which represents the first such case identified beyond the Local Group. The bright giant HII region PES 1, comparable in H{alpha} luminosity to NGC 595 in M 33, is found to host a minimum of 17 WR stars. The remaining photometric candidates generally display photometric properties consistent with WN stars, such that we expect a global WR population of ~115 stars with N(WR)/N(O)~0.01 and N(WC)/N(WN)~0.4.
- ID:
- ivo://CDS.VizieR/J/A+AS/136/35
- Title:
- WR galaxies and HII regions catalog
- Short Name:
- J/A+AS/136/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new compilation of Wolf-Rayet (WR) galaxies and extra-galactic HII regions showing broad He II {lambda}4686 emission drawn from the literature. Relevant information on the presence of other broad emission lines (N III {lambda}4640, C IV {lambda}5808 and other) from WR stars of WN and WC subtypes, and other existing broad nebular lines is provided. In total we include 139 known WR galaxies. Among these, 57 objects show both broad He II {lambda}4686 and C IV {lambda}5808 features. In addition to the broad (stellar) He II {lambda}4686 emission, a nebular He II component is well established (suspected) in 44 (54) objects. We find 19 extra-galactic HII regions without WR detections showing nebular He II {lambda}4686 emission. The present sample can be used for a variety of studies on massive stars, interactions of massive stars with the ISM, stellar populations, starburst galaxies etc. The data is accessible electronically and will be updated periodically
- ID:
- ivo://CDS.VizieR/J/A+A/561/A28
- Title:
- WSRT HI data cubes of the dwarf galaxy UGCA 105
- Short Name:
- J/A+A/561/A28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Owing to their shallow stellar potential, dwarf galaxies possess thick gas disks, which makes them good candidates for studies of the galactic vertical kinematical structure. We present 21cm line observations of the isolated nearby dwarf irregular galaxy UGCA 105, taken with the Westerbork Synthesis Radio Telescope (WSRT), and analyse the geometry of its neutral hydrogen (HI) disk and its kinematics. The galaxy shows a fragmented HI distribution. It is more extended than the optical disk, and hence allows one to determine its kinematics out to very large galacto- centric distances. The HI kinematics and morphology are well-ordered and symmetric for an irregular galaxy. The HI is sufficiently extended to observe a substantial amount of differential rotation. Moreover, UGCA 105 shows strong signatures for the presence of a kinematically anomalous gas component. Performing tilted-ring modelling by use of the least-squares fitting routine TiRiFiC, we found that the HI disk of UGCA 105 has a moderately warped and diffuse outermost part. Probing a wide range of parameter combinations, we succeeded in modelling the data cube as a disk with a strong vertical gradient in rotation velocity (~-60km/s/kpc), as well as vertically increasing inwards motion (~-70km/s/kpc) within the radius of the stellar disk. The inferred radial gas inflow amounts to 0.06M_{sun}_/yr, which is similar to the star formation rate of the galaxy. The observed kinematics are hence compatible with direct or indirect accretion from the intergalactic medium, an extreme backflow of material that has formerly been expelled from the disk, or a combination of both.
- ID:
- ivo://CDS.VizieR/J/A+A/527/A90
- Title:
- WSRT Virgo HI filament survey
- Short Name:
- J/A+A/527/A90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of neutral hydrogen can provide a wealth of information about the kinematics of galaxies. To learn more about the large-scale structures and accretion processes, the extended environment of galaxies have to be observed. Numerical simulations predict a cosmic web of extended structures and gaseous filaments. To observe the direct vicinity of galaxies, column densities have to be achieved that probe the regime of Lyman limit systems. Typically, HI observations are limited to a brightness sensitivity of N_HI_~10^19^cm^-2^, but this has to be improved by ~2 orders of magnitude. With the Westerbork Synthesis Radio Telescope (WSRT), we mapped the galaxy filament connecting the Virgo Cluster with the Local Group. About 1500 square degrees on the sky was surveyed with Nyquist sampled pointings. By using the WSRT antennas as single-dish telescopes instead of the more conventional interferometer, we were very sensitive to extended emission. The survey consists of a total of 22000 pointings, and each pointing was observed for two minutes with 14 antennas.
- ID:
- ivo://CDS.VizieR/J/A+A/528/A28
- Title:
- WSRT Virgo HI filament survey. II.
- Short Name:
- J/A+A/528/A28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The extended environment of galaxies contains a wealth of information about the formation and life cycle of galaxies which are regulated by accretion and feedback processes. Observations of neutral hydrogen are routinely used to image the high brightness disks of galaxies and to study their kinematics. Deeper observations will give more insight into the distribution of diffuse gas in the extended halo of the galaxies and the inter-galactic medium, where numerical simulations predict a cosmic web of extended structures and gaseous filaments. To observe the extended environment of galaxies, column density sensitivities have to be achieved that probe the regime of Lyman limit systems. HI observations are typically limited to a brightness sensitivity of NHI~10^19^cm^-2^, but this must be improved upon by ~2 orders of magnitude.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/43
- Title:
- WWFI g'-band obs. of bright cluster galaxies
- Short Name:
- J/ApJS/247/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of 170 local (z<~0.08) galaxy clusters in the northern hemisphere have been obtained with the Wendelstein Telescope Wide Field Imager (WWFI). We correct for systematic effects such as point-spread function broadening, foreground star contamination, relative bias offsets, and charge persistence. Background inhomogeneities induced by scattered light are reduced down to {Delta}SB>31 g' mag/arcsec^2^ by large dithering and subtraction of night-sky flats. Residual background inhomogeneities brighter than SB_{sigma}_<27.6 g' mag/arcsec^2^ caused by galactic cirrus are detected in front of 23% of the clusters. However, the large field of view allows discrimination between accretion signatures and galactic cirrus. We detect accretion signatures in the form of tidal streams in 22%, shells in 9.4%, and multiple nuclei in 47% of the brightest cluster galaxies (BCGs) and find two BCGs in 7% of the clusters. We measure semimajor-axis surface brightness profiles of the BCGs and their surrounding intracluster light (ICL) down to a limiting surface brightness of SB=30 g' mag/arcsec^2^. The spatial resolution in the inner regions is increased by combining the WWFI light profiles with those that we measured from archival Hubble Space Telescope images or deconvolved WWFI images. We find that 71% of the BCG+ICL systems have surface brightness (SB) profiles that are well described by a single Sersic function, whereas 29% require a double Sersic function to obtain a good fit. We find that BCGs have scaling relations that differ markedly from those of normal ellipticals, likely due to their indistinguishable embedding in the ICL.
